The present invention relates to an offshore tower assembly and, more specifically, to apparatus and methods for anchoring an offshore tower to a earth earch formation.
Numerous offshore activities, such as those relating to the exploration for, and recovery of, offshore oil deposits for example, require the use of water-based facilities for housing equipment and personnel. In this connection, the recovery of oil deposits from submerged earth formations is generally carried out from a tower which is anchored to the submerged earth formation and which includes a platform disposed above the water surface. In order to provide stability and safety for the offshore operations, the tower must be firmly anchored relative to the submerged earth formation.
One conventional technique for anchoring an offshore tower to a submerged earth formation comprises driving a plurality of pilings into the earth formation and operably coupling these pilings to the legs of the tower. Thus the tower is, in effect, pinned to the water bed. The pilings can be affixed within the submerged earth formation by embedding the pilings in grouting material such as concrete or cement. Attention is directed to techniques described in U.S. Pat. Nos. 3,209,544 (issued Oct. 5, 1965); 3,315,473 (issued Apr. 25, 1967); 3,488,967 (issued Jan. 13, 1970); 3,528,254 (issued Sept. 15, 1970); 3,585,801 (issued June 22, 1971); and 3,677,113 (issued July 18, 1972), as being exemplary of such practice.
Once erected, the tower will likely be subjected to the effects of rough waves, high winds, and other natural and operations-related phenomenon which impart relatively high tensile and compressive stressing on the anchoring piles. Such high stressing is especially prevalent in the North Sea, for example.
In order to strengthen the grouted pilings to more effectively resist these loads, it is conventional to apply reinforcing structure to the grouting material. Such reinforcement has been heretofore accomplished, in one known technique, by embedding within the grouting material a plurality of metal rods, or re-bars, held together by a cage structure of some sort. This arrangement is necessarily long in size and typically is extremely flexible and very hard to transport and manipulate. Much difficulty is usually encountered when trying to pick up such an arrangement from a barge deck and lower it through water and into a piling casing. The effect of these wasted man-hours is especially felt in conjunction with the high cost associated with offshore tower operations.
In addition, bell-shaped grouted footings may be employed to anchor the pilings to the water bed. Since relatively short pilings may be used in conjunction with such footings, the importance of establishing a secure connection between the piling and the bell footing is amplified.
It is, therefore, an object of the present invention to obviate or minimize problems of the previously discussed type.
It is another object of the invention to maximize the strength and integrity of an offshore, anchored foundation piling.
It is yet another object of the invention to provide novel apparatus and methods for reinforcing offshore, grout-held foundation pilings.
It is a further object of the invention to provide such methods and apparatus which are economical and uncomplicated and which augment the anchoring action heretofore realized.
It is still another object of the invention to maximize the connection between a piling and a bell footing.
It is a further object of the invention to provide such methods and apparatus which entail a metallic reinforcement tube encased within a tubular piling and a bell footing, and spiral weld beads on the tubular elements embedded within grouting material.